This invention relates to roofing shingles, and more particularly to a method of reducing humping of roofing shingles.
It is well known in the roofing industry that irregularity or variation in shingle design provides a roof that is aesthetically pleasing and in popular demand. Mass produced asphalt roofing shingles of the ordinary three-tab variety, when placed on the roof, result in a roof that sometimes appears flat, dimensionless and uninteresting. Shingle manufacturers have attempted to provide a better appearance to such roofs by using variations in the thickness and in the tab cutout design of shingles. The goal is to produce a random looking sequence or pattern of shingles on the roof, similar to the appearance given by a roof shingled with wood shingles having varying widths, lengths and thicknesses.
Innovations to improve the random-like character of shingles include the use of laminated shingles. A common type of laminated shingle consists of an overlay having tabs and cutouts in the exposed portion of the shingle, and an underlay adhered to the bottom of the overlay below the tabs and cutouts. The laminated shingle includes laminated or double-layered portions where the overlay and underlay overlap, and nonlaminated or single-layered portions where they do not overlap. The laminated portions include the areas of the tabs, and a longitudinal central area of the shingle between the inner ends of the cutouts and the inner end of the underlay. The nonlaminated portions include the areas of the cutouts, and the area of the shingle that does not include the underlay.
After manufacture, the laminated shingles are packaged in a stack or bundle of the shingles. The laminated shingles are often stacked by turning every other shingle 180xc2x0 relative to the adjacent shingles. This stacking method minimizes uneven build in the bundle caused by the difference in thickness between the area of the shingle that includes the underlay and the area that does not include the underlay. However, a problem occurs along the central area of the bundle because the longitudinal central areas of the shingles are double-layered whereas the cutout areas of the shingles on the sides of the central areas are single-layered. The difference in thickness causes an unsightly hump or ridge along the central area of the bundle that becomes progressively higher as the number of shingles in the bundle is increased. When multiple shingle bundles are stacked on a pallet, the humps amplify themselves and can cause unsightly pallet build, instability of the stacked bundles, and high contact pressures at the intersections of the overlapping bundles. The high contact pressures can cause shingle deformation and sticking between individual shingles.
The difference in thickness of different portions of the laminated shingles is not the only cause of humping of the shingles. The overlay and underlay of the laminated shingle are usually joined together by several adhesive beads. The adhesive beads can cause humping of the shingles because of the thickness of the beads.
Further, the humping problem is not limited to laminated shingles. Both laminated shingles and single-layered (xe2x80x9cthree-tabxe2x80x9d) shingles often include a sealant bead on the top of the shingle to hold down the tabs of the adjacent shingle when the shingles are installed on a roof. The sealant beads can also cause humping of the shingles.
The prior art neither mentions the problem of humping nor suggests any method of reducing the problem. For example, U.S. Pat. No. 5,102,487 to Lamb, U.S. Pat. No. 4,233,100 to Cunningham et al., and U.S. Pat. No. 3,921,358 to Bettoli disclose laminated roofing shingles and methods of producing the shingles, but the patents do not address humping of the shingles.
U.S. Pat. No. 4,717,614 to Bondoc et al. discloses a laminated roofing shingle in which the asphalt coating is applied thicker on the tab portion of the overlay than the headlap portion of the overlay. The purpose of this structure is to accentuate the difference in thickness between the overlay and the underlay, in order to improve the appearance of the shingle on the roof. There is no suggestion of the problem of humping or any method of reducing the problem. Therefore, it would be desirable to provide a method of reducing humping of roofing shingles.
The above object as well as others not specifically enumerated are achieved by a method of reducing humping of a laminated roofing shingle when the shingle is stacked with others of the shingle. The shingle includes a longitudinal central area having an overlay laminated with an underlay. The method involves providing a depression in the shingle that extends through at least a portion of the central area.
In another embodiment, the invention is a method of reducing humping of a laminated roofing shingle including an overlay, an underlay, and an adhesive between the overlay and the underlay in an area of the shingle. The method involves providing a depression in the shingle that extends through at least a portion of the adhesive area.
In a further embodiment, the invention is a method of reducing humping of a roofing shingle having a sealant in an area of the shingle. The method involves providing a depression in the shingle that extends through at least a portion of the sealant area.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.